Download Atma-Sphere MP-3 Owner`s manual

1742 Selby Av.
St. Paul, MN 55104 651­690­2246
atma­sphere.com
Atma-Sphere MUSIC PREAMPLIFIER
model MP-3
OWNER'S MANUAL
Please study this document carefully before using equipment
CONGRATULATIONS!
You have purchased one of the world's finest preamplifiers and certainly one of
the most unique. It was over fifteen years in development and represents a
level of performance that others will be struggling to achieve for years to
come. At the time of this writing, it is the only fully balanced differential
vacuum tube design in the world and undoubtedly heralds a new breed. You do not
have to wait all you have to do is set the preamplifier up by following the
simple instructions in this manual.
Every part of the preamplifier has been extensively tested and engineered so
the product will perform flawlessly for years to come, with little if any
service.
Please read the manual carefully and follow the instructions closely. If you
have any questions, do not hesitate to contact your dealer or Atma-Sphere Music
Systems, Inc.. Here's to many years of happy listening!
Sincerely,
Ralph Karsten
Atma-Sphere Music Systems, Inc., 1742 Selby Av., St. Paul, MN 55104
651.690.2246
LIMITED WARRANTY ON Atma-Sphere Music Systems, Inc. Products
This warranty on your Atma-Sphere Music Systems, Inc. product, which is
distributed and warranted by Atma-Sphere Music Systems, Inc., shall remain in
effect for three (3) years from the date of consumer purchase, provided the
enclosed registration form is completed and returned to Atma-Sphere Music
Systems, Inc. within ten days of purchase.
WHAT IS COVERED:
Except as specified below, this warranty covers all defects in materials and
workmanship. The following are NOT covered by the three year limited warranty:
* Tubes are covered for 90 days, with the following exclusions, as per the rest
of the warranty:
* Damage occurring during shipment (present claims to carrier).
* Damage resulting from failure or inability to follow proper instructions.
* Damage resulting from the performance of repairs or modifications by other than
Atma-Sphere Music Systems, Inc..
WHAT WE WILL PAY FOR:
Atma-Sphere Music Systems, Inc. will pay for all labor and material expenses
for repairs covered by this warranty.
HOW TO OBTAIN WARRANTY SERVICE:
If your unit requires repairs covered by this warranty, you MUST obtain a
return authorization number from Atma-Sphere Music Systems, Inc.. You are
responsible for transporting the unit to Atma-Sphere Music Systems, Inc., 1742
Selby Av., St. Paul, Minn. 55104. You must pay the initial shipping charges,
but Atma-Sphere Music Systems, Inc. will pay the return charges, if the repairs
are covered by the warranty. All products MUST be shipped in the original
carton(s) or in replacement cartons supplied by Atma-Sphere Music Systems,
Inc.. Contact Atma-Sphere Music Systems, Inc. for replacement cartons and cost.
LIABILITY IS LIMITED TO THE REPAIR OR REPLACEMENT, AT OUR OPTION, OF ANY
DEFECTIVE PRODUCT AND SHALL IN NO EVENT INCLUDE INCIDENTAL OR CONSEQUENTIAL
DAMAGE OF ANY KIND.
This warranty is transferable. Implied warranties of merchantability and
fitness for a particular purpose are limited in duration to the length of this
warranty. This warranty sets forth all expressed warranties made with regard to
the above-referenced product. We neither assume nor authorize any other
liability in connection with the sale or any shipment of products. This
warranty gives you specific legal rights and you may also have other rights
which vary from state to state. We reserve the right to make changes and
improvements in our products without incurring any obligation to similarly
alter products previously purchased.
MUSIC PREAMPLIFIER SETUP AND OPERATION
Unpack the preamplifier carefully and save the packaging containers for future
shipment if required.
During operation, the MP3 gets warm. Adequate ventilation is mandatory. If the
preamplifier is to be placed in a shelf or rack mount system, allow for at
least 2 inches of open space above the unit. Make sure that the preamplifier is
at least a foot away from any power supply, to avoid hum problems.
After the preamplifier is properly positioned, make sure that the power switch
is in the OFF position. Connect the cables for the various components to be
used with the preamplifier.
For sonic performance reasons, the MP3 does not use a muting circuit! Allow the
preamplifier to warm up and stabilize before energizing your power amplifiers.
A muting circuit is not used as it would interfere with the servo loop
operation in the output section of the preamp. Its presence in the circuit
would be audible as well. Although the DC offsets generated during warmup are
low level, they could be a problem for some amplifiers and speakers.
WARNING! DO NOT TURN ON THE AMPLIFIERS IN YOUR SYSTEM UNTIL THE PREAMPLIFIER
IS WARMED UP AND STABILIZED! DAMAGE TO SPEAKERS, AMPLIFIERS OR BOTH MAY
RESULT!
Get in the habit of turning down the volume or switching to an unused input
anytime you turn your amplifier on, when you change a record, etc.
After the preamplifier is turned on, it takes about 30 seconds before it is
ready for use. During the warmup of the preamplifier, one or both of the "DC
OFFSET" LEDs on the front panel may light up. This indicates that the servo
circuit has detected a DC voltage at the output of the preamp and is
trying to correct it. If the indicator stays lit for more than a minute, a
fault is indicated and the preamplifier must be turned off immediately to
prevent damage to associated equipment. Refer to the troubleshooting page in
this manual. It is normal for the indicators to flicker at high volume
settings. The preamplifier will sound significantly better after about 45
minutes of operation.
OPERATING NOTES
Normally the preamplifier can be left on all the time, although be aware that
modern 12AT7s will last only about 3,000 hours on the outside (about 5 months).
Be sure to provide for adequate ventilation. The 12AT7 phono tubes should be
checked every 5 months if the unit is left on continuously. The unit will
sound substantially better three hours after turn-on.
The MP3 may be used with a low impedance (600 ohm) load at the input of the
power amplifier which can be used to reduce hum and buzz.
Usually you will have to adjust the GAIN TRIM for proper soundstage
(balance)effect, because the MP3 is a zero feedback design. Various tubes will
result in differing amounts of gain between left and right channels. Operate
the control SLOWLY. The GAIN TRIM controls are not in the audio path. They may
generate a temporary DC offset while they are operated. This effect will vary
depending on the balance of the sections in the 12AU7 used in the high level
section.
Due to the nature of the MP3, expensive cables between the preamplifier and
power amplifier are less important. The cable differences you hear will be
minor compared to single-ended cables. Thus we have no recommendation for
cables to be used between the preamplifier and power amplifier. On the other
hand, the input cables may be very critical, depending on the source.
NOTE:
Some flashing of the DC Offset L.E.D.s is normal at high volumes.
PHONOGRAPH HOOKUP
Almost all phonograph cartridges are balanced sources. Thus the MP3 allows you
to set up your turntable as a fully-balanced source, with considerable sonic
advantage. For best results, follow the connection scheme outlined below:
1) Use a cable that has two signal conductors PLUS a shield for each channel.
The two conductors are for the plus and minus outputs of the cartridge, and the
shield connection becomes the tone arm/turntable ground connection and is
common to BOTH channels.
2) Pin number one of any XLR connection should always be ground as per industry
standard.
3) Pin two of the XLR phono input corresponds to the "+" or non-inverting
output of the cartridge, and pin three is the "" or inverting output of the
cartridge. Absolute system phase can be corrected from the front panel.
4) There is no need for an independent ground wire from the arm to the preamp.
If you set up the cable correctly, there will be little or no hum. Many tone arms use
a five pin connector that plugs into the bottom of the arm. If this is the case in
your system, you may order a tone arm cable with the right connections from almost any
cable manufacturer. If your arm has RCA connectors at the output, an adapter cable can
be made that will work. The shield connection of the RCA must become the connection to
pin 3 of the XLR connector, and the tone arm ground connection should be made as
described above. ON NO ACCOUNT should you allow the shield connection of the RCA to
become the shield for the cable, as this may result in a loud hum.
Cartridge loading is achieved by installing resistors on the loading terminal on the
rear panel. A screwdriver is all that is needed for attachment. You will have to
experiment to obtain the correct value.
Avoid using NOS 12AT7s in the MP3. Generally, and despite claims to the contrary, most
such tubes are too noisy for proper operation in the MP3! Please purchase new 12AT7s
from your dealer or Atma-Sphere Music Systems, Inc.. Most 12AT7s tend to get noisy
after about 3 thousand hours so if you leave the preamp on 24 hours a day the phono
tubes should be replaced every 34 months. They will last longer if the preamp is
turned off when not in use. In any event, be VERY suspicious of any NOS 12AT7s. Most
of them are unacceptable.
For very low output cartridges you may wish to have the step-up transformer option
installed. Contact your dealer for details.
High-Level Hookup
The auxiliary inputs are high impedance. Thus you may use any input as a source
for the MP3. If you are using a low impedance source, a low impedance
termination is recommended for better sound. A single-ended source can also be
used, by applying the signal between either pin two or pin three of the input
XLR, and ground. The unused input (pin three or pin two, respectively), may
have to be shorted out to prevent noise. Pin two of all the XLR inputs is the
non-inverting input, per industry standard.
The tape outputs are high impedance. Use a high quality cable for best results
and keep the cable as short as possible. The minimum drive impedance is
20Kohms. The tape 2 output is inverted while tape 1 is non-inverted.
The tape monitors are a single-ended, non-inverting, high impedance input.
NOTES ON TUBES
1) The 12AT7s in the rear left of the board are the most critical for low noise
phono operation.
2) The constant current source tube The 7th 12AT7 by itself in the rear) is
outside of the signal path.
3) Matched sections in the 12AU7s of the high level section will
reduce DC offset during operation of the front panel GAIN TRIM controls.
4) Tube damping rings are recommended.
5) Do not remove tubes while unit is operating. Hazardous or lethal voltages
are present!
6) NEVER use Tweek on vacuum tubes.
7) Long live analog!
TROUBLESHOOTING TIPS
Bottom front panel LED won't light up: Check the rear panel AC connector and
verify that the power cord is plugged in. If so, the internal 1.5Amp SLOW BLOW
(.75A if 235 Volts) fuse may be blown.
Buzz, hum and/or RF interference: Make sure that the power cord is plugged into
a properly grounded outlet and that no other equipment in the system is
grounded (resulting in a ground loop). Sometimes RF can get into the phonograph
through poorly shielded wiring in or from the tone arm. This is common with
modern straight-tracking arms. Buzz can also occur if the input of the
amplifier is not properly balanced. This can occur if the amplifier has an RF
filter at its input that is only active on the non-inverting input. There are
quite a few transistor amps with balanced inputs that are set up this way.
Distortion: Check the output tube (6SN7) and the associated 12AU7 for defects.
Also pin 3 or pin 2 of the XLR may be shorted to ground.
Both channels dead, unit lights up: There is a fuse located on the rear right
side edge of the circuit board (as you face the front of the unit). Replace
with the same type slow-blow fuse (.75 Amp for 117 Volt units, .35 Amp for 230
Volt units). If you are not qualified, do not remove the cover. Hazardous or
lethal voltages are present with the cover removed. Refer servicing to
qualified service personnel.
Ringing or 'bell' sound when operating volume (microphonics): Usually the 12AU7
in the line stage is the most likely to cause this fault. The 12AT7s in the
phono section can do this too. If the MP3 is OK on AUX inputs, but rings on the
phono, then a 12AT7 is most likely at fault.
LED lit up continuously: Check the 6SN7 in the channel associated with the LED.
If only channel is lit, try swapping the left and right 6SN7s. The lit LED
should now be in the other channel. If the LED remains lit, replace the TLO82
opamp ICs beside the associated 6SN7. They are in sockets and the ICs are
available from Radio Shack or other electronic supply houses.
NEVER, EVER, USE TWEEK ON TUBE SOCKETS! Tweek is an organic compound and is
capable of forming resistance paths if it breaks down.
If none of these suggestions help, please contact your dealer or Atma-Sphere
Music Systems, Inc..
MORE TIPS AND TWEAKS
You can reduce the noise level beyond the specification by using low noise tubes. When
ordering from any source, specify tubes for a differential circuit (matched tube
sections). We have found that the 12AT7 at the input of the phonograph section, and
the 12AU7 at the input of the high-level section are perhaps the most audible.
We recommend line conditioning. The fifth harmonic of the powerline frequency has been
shown to be far more problematic for good sound then all other types of powerline
problems (RF, spikes, etc.) put together. Be sure that the conditioner you use can
filter line frequency harmonics, particularly the fifth (300 Hz on 60Hz line).
We have found that the power cord can have audible effects! A good cable is
recommended.
The Sound Anchors equipment stand is the finest we have seen. It is highly
recommended. Use it in conjunction with the Ultra Resolution Technologies vibration
damping platform. NavCom Silencers or other anti-vibration pads are also recommended.
Tube damping rings are highly recommended.
A cartridge with .3mv or more is recommended, unless you have the stepup transformer
option.
NOTES
WARRANTY REGISTRATION FORM
IMPORTANT: This form must be filled out and returned to Atma-Sphere Music
Systems, Inc. within 10 days of purchase to validate the warranty! Please type
or print clearly.
NAME__________________________________________________________________________________
Address_______________________________________________________________________________
City or town _________________________________State___________zip code________________
Country_______________________________________________________________________________
Name of
dealership____________________________________________________________________________
Model
MP-3
Date of purchase___________serial #_________price paid______________
Optional section for our records and information:
Comments concerning your
dealer________________________________________________________________________________
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Comments concerning this product______________________________________________________
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list the components in your system___________________________________________________
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comments,suggestions__________________________________________________________________
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MAIL TO:
Atma-Sphere Music Systems, Inc.,
1742 Selby Av.,
St. Paul,
MN
55104
USA